The measurement of hydrogen peroxide concentration in aqueous systems is important in many cases such as, for instance, when using H.sub.2 O.sub.2 as an oxidant for the treatment of effluents (see W. H. KIBBEL, Peroxide Treatment of Industrial Waste Waters, Industrial Water Engineering, August-September 1976) and in medical diagnostic analysis. Thus, in connection with the medical aspect, many analytical techniques exist based on enzymatic oxidation reactions which involve the quantitative production of H.sub.2 O.sub.2. Such techniques are particularly valuable because of the highly selective and sensitive behavior of some enzymatic systems toward specific substrates.
Thus, it is well-known to use an "oxidase" for catalyzing the quantitative oxidation of a substrate with the formation of a corresponding amount of hydrogen peroxide. This H.sub.2 O.sub.2 can be thereafter measured by another enzymatic reaction in which an indicator dye is oxidized by this H.sub.2 O.sub.2 in the presence of a peroxidase whereby the intensity of the color developped is a measure of the amount of the H.sub.2 O.sub.2 present in the system and, consequently, a measure of the amount of the substrate originally present which generated the said H.sub.2 O.sub.2 upon oxidation.
The "oxidase" enzymes suitable for such determination are usually named from the type of substrate they can act upon; thus, glucose oxidase specifically catalyzes the oxygen oxidation of glucose into gluconic acid with liberation of H.sub.2 O.sub.2 ; cholesterol oxidase acts similarly toward cholesterol, etc.